<template>
<!-- vue封装轮播图插件 -->
  <div class='xtx-carousel' @mouseenter="stop()" @mouseleave="start()">
    <ul class="carousel-body">
       <li class="carousel-item" v-for="(item,i) in lunbotu" :key="i" :class="{fade:index===i}">
        <RouterLink to="/">
          <img :src="item.imgUrl" alt="">
        </RouterLink>
      </li>
    </ul>
    <a href="javascript:;" class="carousel-btn prev" @click="qiehuan(-1)"><i class="iconfont icon-angle-left"></i></a>
    <a href="javascript:;" class="carousel-btn next" @click="qiehuan(1)"><i class="iconfont icon-angle-right"></i></a>
    <div class="carousel-indicator">
     <span v-for="(item,i) in lunbotu" @click="index = i" :key="i" :class="{active:index===i}"></span>
    </div>
  </div>
</template>

<script>
import { ref, watch, onUnmounted } from 'vue'
export default {
  name: 'XTXLunboBanner',
  props: {
    lunbotu: {
      type: Array,
      default: () => []
    },
    duration: { // 轮播图时间
      type: Number,
      default: 3000
    },
    autoPlay: {
      type: Boolean, // 是否自动播放
      default: false
    }
  },
  setup (props) {
    // 默认显示的图片的索引
    const index = ref(0)
    // 自动播放
    let timer = null
    const autoPlayFn = () => {
      clearInterval(timer) // 防止定时器叠加
      timer = setInterval(() => {
        index.value++
        if (index.value >= props.lunbotu.length) {
          index.value = 0
        }
      }, props.duration)
    }// 监听事件
    watch(() => props.lunbotu, (newVal) => {
      // 有数据&开启自动播放，才调用自动播放函数
      if (newVal.length && props.autoPlay) {
        index.value = 0 // 从第一张开始
        autoPlayFn() // 调用播放
      }
    }, { immediate: true })
    // 鼠标进入停止，移出开启自动，前提条件：autoPlay为true
    const stop = () => {
      if (timer) clearInterval(timer) // 定时器停止
    }
    const start = () => { // 离开轮播图开始播放
      if (props.lunbotu.length && props.autoPlay) {
        autoPlayFn() // 重新调用
      }
    }
    // 上一张下一张
    const qiehuan = (i) => {
      const newIndex = index.value + i // 先判断值是否超出轮播图图片的范围
      if (newIndex >= props.lunbotu.length) {
        index.value = 0 // 超出时重新赋值为零
        return
      }
      if (newIndex < 0) {
        index.value = props.lunbotu.length - 1
        return // 小于零时，设为最大值
      }
      index.value = newIndex // 最后的结果进行赋值
    }
    // 卸载时 清除组件消耗，清理定时器
    onUnmounted(() => {
      clearInterval(timer)
    })
    return { index, stop, start, qiehuan }
  }
}

</script>
<style scoped lang="less">
.xtx-carousel{
  width: 100%;
  height: 100%;
  min-width: 300px;
  min-height: 150px;
  position: relative;
  .carousel{
    &-body {
      width: 100%;
      height: 100%;
    }
    &-item {
      width: 100%;
      height: 100%;
      position: absolute;
      left: 0;
      top: 0;
      opacity: 0;
      transition: opacity 0.5s linear;
      &.fade {
        opacity: 1;
        z-index: 1;
      }
      img {
        width: 100%;
        height: 100%;
      }
    }
    &-indicator {
      position: absolute;
      left: 0;
      bottom: 20px;
      z-index: 2;
      width: 100%;
      text-align: center;
      span {
        display: inline-block;
        width: 12px;
        height: 12px;
        background: rgba(0,0,0,0.2);
        border-radius: 50%;
        cursor: pointer;
        ~ span {
          margin-left: 12px;
        }
        &.active {
          background:  #fff;
        }
      }
    }
    &-btn {
      width: 44px;
      height: 44px;
      background: rgba(0,0,0,.2);
      color: #fff;
      border-radius: 50%;
      position: absolute;
      top: 228px;
      z-index: 2;
      text-align: center;
      line-height: 44px;
      opacity: 0;
      transition: all 0.5s;
      &.prev{
        left: 20px;
      }
      &.next{
        right: 20px;
      }
    }
  }
  &:hover {
    .carousel-btn {
      opacity: 1;
    }
  }
}
</style>
